G+7 Storied Building of ht 8@4m. What do you do if you found accumulated drift in columns on G+3rd floor is 80mm? Assume equal drift in each floors.

You have to provide more information, maybe an elevation drawing, and a plan showing which columns the drift has occurred in? Regardless, I think you'll have to o back to the drawing board, you will need to model the drift, and find if the slab can efficiently handle the load transfers of the eccentric loads. If they can't, then you will need to develop a solution specific to your structure to counter that.